The conventional method of adding hydropower generation capability to a non-electrified dam is to remove a portion of the dam and then (1) to build a structure to provide the water conduits to drive conventional turbines, (2) to build a powerhouse to protect the turbines and generators, and (3) to provide a crane to install and service this equipment. It requires drying out the location by means of temporary or cofferdams upstream and downstream of the dam to enable placement of the civil works structure on the bottom of the waterway. A conventional turbine system places an unsightly building on an otherwise low-profile dam structure, and installation is an expensive and time-consuming process.
Other conventional methods involve the use of conventional combined turbine/generators, also called bulb turbines, which are heavy, expensive and less efficient than a newly-developed turbine/generators that weigh much less and install on a bulkhead, thereby avoiding the expense of civil works and cofferdams. This newly-developed turbine is the subject of U.S. Pat. Nos. 7,235,894, 7,385,303, 8,536,723 and U.S. patent application Ser. No. 13/356,288. The system, by virtue of its low weight and small dimensions, allows installation in single or multiple units on a movable gate, thereby allowing for the movable gate to be raised into a maintenance position for the turbine/generator to be serviced or replaced in short order (less than one day), avoiding long-term interruption to power generation.
The mitigation or elimination of some ecological threats created by conventional systems is important in that the present invention makes possible the avoidance of interference with wildlife.
The prior art generally involves systems that are made of steel or bronze and are very heavy. U.S. Pat. No. 5,825,094 discloses a gate structure that is extremely heavy and not practical to build, and using such a gate structure with prior (very heavy) turbines would involve cost which would never be able to be recovered by revenue from electricity generated. Further, such an approach would require an outsized lifting system to raise the gate structure with turbines installed above flood level. Service and maintenance would be extremely difficult since all runners have mechanical drive lines to the generators which use hypoid gear drives. Failure of one of the units stops all other connected turbines, and repair requires the complete unit to be taken out for repair.
Many patents such as U.S. Pat. No. 6,146,096, U.S. Pat. No. 6,281,597 and U.S. Pat. No. 7,372,172 refer to using existing dam gate installations to provide added power generation and the use of multiple self-contained, bulb-type turbine/generators placed in a matrix within a movable gate or pod to provide a low-head hydropower generation system without the need for a powerhouse. Such systems are severely limited by the metallic turbine/generators and fail to address efficiency and variation in flow rate to maintain efficiency. Also, these systems rely on existing crane lifting systems for movement of the turbine matrices. Since heavy metallic turbine/generators require the use of a larger number of smaller units to generate the required level of power, efficiency of the overall system suffers.
U.S. Pat. No. 7,372,172 is characteristic of such an approach whereby a limited number of small metallic turbine/generators are placed in an enclosure, pod or container. This patent discloses a lifting mechanism substantially different for the present invention, and weight of the structures which must be lifted is extremely high.
The present invention incorporates patented and patent-pending low-weight turbine/generators that can be installed in gates and a unique lifting mechanism utilizing rotational movement and capable of spanning the width between piers of a dam agate section. In contrast to the conventional bulb-type matrix turbines, the present invention allows for higher power, larger diameter, low weight turbine/generators to be employed.
In addition, because of the sensitive state (due to age and poor maintenance) of the present dam system in the United States, the modification of an existing non-power-producing dam, however small, creates a concern over the effect of modification such that permission to make changes to add hydropower generation may be denied. The present patent provides a system that does not attach to or alter an existing dam structure in any way while cooperating with the existing dam equipment to provide maximum capacity power generation.